Therapeutic targeting of prenatal pontine ID1 signaling in diffuse midline glioma

BACKGROUND

Diffuse midline gliomas (DMG) are highly invasive brain tumors with rare survival beyond two years past diagnosis and limited understanding of the mechanism behind tumor invasion. Previous reports demonstrate upregulation of the protein ID1 with H3K27M and ACVR1 mutations in DMG, but this has not been confirmed in human tumors or therapeutically targeted.

METHODS

Whole exome, RNA, and ChIP-sequencing was performed on the ID1 locus in DMG tissue. Scratch-assay migration and transwell invasion assays of cultured cells were performed following shRNA-mediated ID1-knockdown. In vitro and in vivo genetic and pharmacologic [cannabidiol (CBD)] inhibition of ID1 on DMG tumor growth was assessed. Patient-reported CBD dosing information was collected.

RESULTS

Increased ID1 expression in human DMG and in utero electroporation (IUE) murine tumors is associated with H3K27M mutation and brainstem location. ChIP-sequencing indicates ID1 regulatory regions are epigenetically active in human H3K27M-DMG tumors and prenatal pontine cells. Higher ID1-expressing astrocyte-like DMG cells share a transcriptional program with oligo/astrocyte-precursor cells (OAPCs) from the developing human brain and demonstrate upregulation of the migration regulatory protein SPARCL1. Genetic and pharmacologic (CBD) suppression of ID1 decreases tumor cell invasion/migration and tumor growth in H3.3/H3.1K27M PPK-IUE and human DIPGXIIIP* in vivo models of pHGG. The effect of CBD on cell proliferation appears to be non-ID1 mediated. Finally, we collected patient-reported CBD treatment data, finding that a clinical trial to standardize dosing may be beneficial.

CONCLUSIONS

H3K27M-mediated re-activation of ID1 in DMG results in a SPARCL1+ migratory transcriptional program that is therapeutically targetable with CBD.

Routine four-quadrant cavity shaving at the time of wide local excision for breast cancer reduces re-excision rate

INTRODUCTION

Breast conservation therapy (BCT) has been shown to have comparable long-term survival outcomes when compared with mastectomy. Clearance of excision margin is one of the mainstays of the surgical treatment, which if not achieved at the first operation of BCT results in the need for subsequent surgery.

METHODS

This study evaluated the impact of routinely taken cavity shavings on re-excision rates. This retrospective two-centre study describes the use of routine four-quadrant cavity shaving in 449 patients with consecutively treated with wide local excision for invasive cancer or ductal carcinoma in situ.

RESULTS

The overall incomplete excision rate was 10.6%. Routine cavity shaving prevented the need for re-excision in 84 patients (18.7%) and identified the need for further re-excision in 33 patients (7.3%). Median time from surgery to radiotherapy was 50 days (range 13-209) for non-re-excised patients versus 78 days (range 47-260) for re-excised patients (p<0.001). Median time to chemotherapy (n=75) was 44 days (range 14-106) for non-re-excised patients versus 56 days (range 35-116) for re-excised patients (p=0.017).

CONCLUSIONS

This study demonstrates that routine cavity shaving decreases re-excision rate in patients treated with wide local excision and prevents delays to adjuvant treatment due to incomplete excision.

CSIG-09. THERAPEUTIC TARGETING OF PRENATAL PONTINE ID1 SIGNALING IN DIFFUSE MIDLINE GLIOMA

Diffuse midline gliomas (DMG) are highly invasive brain tumors with rare survival beyond two years past diagnosis. The mechanism behind tumor invasion is currently not well understood. Previous reports demonstrate upregulation of the protein ID1 with H3K27M and ACVR1 mutations in DMG, but this has not been confirmed in human tumors or therapeutically targeted. Whole exome, RNA, and ChIP-sequencing were performed on the ID1 locus in DMG tissue. Scratch-assay migration and transwell invasion assays of cultured cells were performed following shRNA-mediated ID1-knockdown. In vitro and in vivo genetic and pharmacologic [cannabidiol (CBD)] inhibition of ID1 on DMG tumor growth was assessed. Additional in vitro experiments were performed to determine a potential mechanism of action for CBD-mediated effects. Self-reported CBD dosing information was collected from DMG patients. We found that increased ID1 expression in human DMG and in utero electroporation (IUE) murine tumors is associated with H3K27M mutation and brainstem location. ChIP-sequencing indicates a similar epigenetically active state at ID1 regulatory regions in human H3K27M-DMG tumors and prenatal pontine cells. Higher ID1-expressing astrocyte-like DMG cells share a transcriptional program with oligo/astrocyte-precursor cells (OAPCs) from the developing human brain and demonstrate upregulation of the migration regulatory protein SPARCL1. Genetic and pharmacologic (CBD) suppression of ID1 decreases tumor cell migration, tumor growth, and to a lesser extent invasion in both murine IUE and multiple patient-derived in vivo DMG models, improving mouse survival. ID1 knockdown significantly decreases the effect of CBD on migration, tumor growth, and invasion. CBD increases reactive oxygen species production, which also affects DMG cell proliferation in a non-ID1 mediated manner. Overall, we find that H3K27M-mediated reactivation of ID1 in DMG results in a SPARCL1+ migratory transcriptional program that is therapeutically targetable with CBD.

TAMI-79. THERAPEUTIC REVERSAL OF PRENATAL PONTINE ID1 SIGNALING IN DIPG

Diffuse intrinsic pontine glioma (DIPG) is a highly aggressive pediatric brain tumor with rare survival beyond two years. This poor prognosis is largely due to the tumor's highly infiltrative and invasive nature. Nearly 80% of DMGs harbor K27M mutation in the genes encoding histone H3.1 (H3F3A) or H3.3 (HISTIH3B), often with concurrent ACVR1 mutation. Inhibitor of DNA-binding (ID) proteins are key transcriptional regulators of genes involved in lineage commitment and are associated with invasiveness and poor clinical outcomes in multiple human cancers. Introduction of H3K27M and ACVR1 mutations increase ID1 expression in cultured astrocytes, but this has not been confirmed in human tumors or targeted therapeutically. We developed an in-utero electroporation (IUE) murine H3K27M-driven tumor model, which demonstrates increased ID1 expression in H3K27M- and ACVR1-mutated tumor cells. Exome and transcriptome sequencing analysis of multi-focal DMG tumors (n=52) and normal brain tissue revealed that increased ID1 expression is associated with H3K27M/ACVR1-mutation and brainstem location, and correlates with poor survival in patients. ChIP-sequencing for H3K27ac and H3K27me3 in multiple DMG tumors (n=5) revealed that the ID1 gene is epigenetically active, which matches the epigenetic state of murine prenatal hindbrain cells. Higher ID1-expressing astrocyte-like DIPG cells share a similar transcriptional program with ID1+/SPARCL1+ positive oligo/astrocyte-precursor (OAPC) cells from the developing human brain and demonstrate upregulation of gene sets involved in regulation of cell migration. Both genetic and pharmacologic [cannabidiol (CBD)] suppression of ID1 result in decreased DIPG cell invasion/migration in vitro and invasion/tumor growth in multiple in vivo models. Mechanistically, CBD reduces proliferation through production of reactive oxygen species. Further, DIPG patients treated off-trial with CBD (n=15) displayed reduced ID1 tumor expression and improved overall survival. In summary, ID1 is upregulated in DIPG through K27M-mediated epigenetic reactivation of a developmental OAPC-like transcriptional state, and ID1-driven invasiveness of DIPG is therapeutically targetable with CBD.

EPCT-07. ID1 IS A KEY TRANSCRIPTIONAL REGULATOR OF DIPG INVASION AND IS TARGETABLE WITH CANNABIDIOL

Diffuse intrinsic pontine gliomas (DIPGs) are lethal pediatric brain tumors with no effective therapies beyond radiation. The highly invasive nature of DIPG is key to its aggressive phenotype, but the factors and mechanisms contributing to this aggressive invasion are unknown. Inhibitor of DNA binding (ID) proteins, key regulators of lineage commitment during embryogenesis, are implicated in tumorigenesis in multiple human solid tumors. Prior work showed that recurrent H3F3A and ACVR1 mutations increase ID1 expression in cultured astrocytes. However, the impact and targetability of ID1 have not been explored in human DIPG. Exome and transcriptome sequencing analyses of multi-focal DIPG tumors and normal brain tissue from autopsy (n=52) revealed that ID1 expression is significantly elevated in DIPG samples. Higher ID1 expression correlates with reduced survival in DIPG patients and increased regional invasion in multi-focal autopsy samples. Analyses of developing mouse brain RNA/ChIP-Seq data revealed high ID1 expression and H3K27ac promoter binding in prenatal hindbrain compared to all other prenatal and postnatal brain regions. ChIP-qPCR for H3K27ac and H3K27me3 revealed that ID1 gene regulatory regions are epigenetically poised for upregulation in DIPG tissues compared to normal brain, regardless of H3/ACVR1 mutational status. These data support that the developing pons is regionally poised for ID1 activation. Genetic (shRNA) ID1 knockdown of primary human H3.3K27M-DIPG cells (DIPG007) resulted in significantly reduced invasion/migration and significantly improved survival of K27M-DIPG mice. Knockdown of ID1 in DIPG cells also resulted in down-regulation of the WNK1-NKCC1 pathway, which regulates tumor cell electrolyte homeostasis and migration. Finally, treatment of DIPG007 cells with cannabidiol (CBD) reduced ID1 levels, viability of DIPG cells and significantly improved survival of K27M-DIPG mice. In summary, our findings indicate that multifactorial (genetic and regional) epigenetic upregulation of ID1 drives DIPG invasiveness; and that targeting ID1 with CBD could potentially be an effective therapy for DIPG.

DIPG-08. ELECTRONIC SEQUENCING PROVIDES OPTIMIZED QUANTIFICATION OF SERIAL, MULTI-GENE MOLECULAR RESPONSE IN THE CSF OF CHILDREN WITH HIGH-GRADE GLIOMA

BACKGROUND

For pediatric high-grade glioma (pHGG), non-invasive methods for diagnosis and surveillance are needed. Tumors release DNA (tDNA) into cerebrospinal fluid (CSF), allowing for detection of tumor-associated mutations by CSF sampling. We hypothesized that direct, electronic analysis of tDNA with a novel, hand-held platform (Oxford Nanopore MinION) could quantify patient-specific CSF tDNA variant allele fraction (VAF) with improved speed and limit of detection compared to established methods.

METHODS

We integrated required multi-timepoint (0, 2, and 6 months) correlate lumbar punctures (LP) in two ongoing pHGG clinical trials. Using Nanopore technology, we performed amplicon-based PCR on CSF tDNA for recurrent mutations from patient samples (n=19) and normal controls. VAF were determined via MinKNOW, Guppy, MiniMap2, and Integrated Genome Browser.

RESULTS

Nanopore CSF tDNA demonstrated improved sensitivity (91%) when compare to NGS sequencing (50%). Nanopore analysis of serially diluted CSF sample demonstrated significantly lower limit of detection (attomolar) than typical NGS sample requirement (nanomolar). H3K27M mutation was reliably detected with 1,000x depth sequencing, which was achieved in less than 15 minutes of sequencing after amplification. Multiplexed Nanopore analysis of H3F3A and HIST1H3B was employed when H3 status was unknown. Serial CSF tDNA analysis confirmed multi-gene (H3F3A K27M, PIK3CA, and TP53) molecular remission in a 17-year-old with thalamic diffuse midline glioma that correlated with sustained clinical response to ONC201 (14 months and ongoing).

CONCLUSIONS

Use of a hand-held, electronic DNA analysis platform allows quantification of multi-gene molecular response with improved speed and limit of detection in the CSF of children with high-grade glioma.

DIPG-59. UPREGULATION OF PRENATAL PONTINE ID1 SIGNALING IN DIPG

BACKGROUND

Diffuse intrinsic pontine gliomas (DIPGs) are lethal pediatric brain tumors with no curative therapies. Inhibitor of DNA binding (ID) proteins are key regulators of gene differentiation during embryogenesis. Previous work has shown that H3F3A and ACVR1 mutations increase ID1 expression in cultured astrocytes, but this has not been validated in human DIPG, nor has the regulation and targetability of ID1 been explored in DIPG.

RESULTS

Analysis of post-mortem tissue and multiple human datasets showed ID1 to be elevated in DIPG, and to correlate with reduced survival. In a multi-focal autopsy of a DIPG case, we also found ID1 expression to be heterogeneous and to correlate with tumor invasion. Chromatin immunoprecipitation qPCR (ChIP-qPCR) revealed elevated H3K27ac and low H3K27me3 at ID1 regulatory regions (enhancers/promoters) in DIPG tissue compared to normal brain, regardless of H3 or ACVR1 mutation status. Analysis of publicly-available ISH and ChIP-sequencing data of developing murine brains revealed H3K27ac at ID1 enhancers to be elevated in the prenatal hindbrain compared to prenatal forebrain and midbrain, and all postnatal brain regions. ID1 shRNA-mediated knockdown of primary human H3K27M DIPG cells (DIPG007) significantly reduced invasion and migration. We also treated DIPG007 cells with cannabidiol (CBD) and found reduced viability at clinically relevant dosing (IC50=2.4 uM) with dose-dependent reduction in ID1 protein.

CONCLUSIONS

These findings indicate that a multifactorial (genetic and regionally-based) epigenetic upregulation of ID1 drives DIPG invasiveness and is targetable with CBD. ID1 knockdown and CBD treatment experiments in murine models of DIPG are ongoing.

TAMI-29. MULTIFACTORIAL UPREGULATION OF ID1 DRIVES DIPG INVASIVENESS AND IS THERAPEUTICALLY TARGETABLE

Diffuse intrinsic pontine gliomas (DIPGs) are lethal brain tumors with no effective therapies other than radiation. Inhibitor of DNA binding (ID) proteins, key regulators of lineage commitment during embryogenesis, are implicated in tumorigenesis in multiple human cancers. Prior work showed that recurrent H3F3A and ACVR1 mutations increase ID1 expression in cultured astrocytes. However, this has not been validated in human DIPG. The regulation and targetability of ID1 in DIPG has not been explored either. Exome and transcriptome sequencing analysis of multi-focal DIPG tumors and normal brain tissue from autopsy (n=52) revealed that ID1 expression is significantly elevated in DIPG tissues. Higher ID1 expression correlates with reduced survival in DIPG patients and increased regional invasion in multi-focal autopsy samples. Analyses of developing mouse brain RNA/ChiP-Seq data revealed high ID1 expression and H3K27ac promoter binding in prenatal hind brain compared to all other prenatal and postnatal brain regions. ChIP-qPCR for H3K27ac and H3K27me3 revealed that ID1 gene regulatory regions are epigenetically poised for upregulation in DIPG tissues compared to normal brain, regardless of H3/ACVR1 mutational status. These data support that the developing pons is regionally poised for ID1 activation. Genetic (shRNA) ID1 knockdown in primary human H3.3K27M-DIPG cells (DIPG007) resulted in significantly reduced invasion and migration in vitro. Additionally, DIPG-ID1-KO cells showed improved sensitivity to radiation therapy. Phospho-kinase array analysis of DIPG cells revealed that Akt and WNK1 activity were significantly downregulated upon ID1 knockdown, which was previously shown in lung tumors. Treatment of DIPG007 cells with cannabidiol (CBD) reduced ID1 expression levels and viability/proliferation of DIPG cells in vitro. ID1 knockdown and CBD treatment studies in vivo are ongoing. In summary, our findings indicate that multifactorial (genetic and regional) epigenetic upregulation of ID1 drives DIPG invasiveness and targeting ID1 using CBD may be a potential strategy for the treatment of DIPGs.

Electronic DNA Analysis of CSF Cell-free Tumor DNA to Quantify Multi-gene Molecular Response in Pediatric High-grade Glioma

PURPOSE

Pediatric high-grade glioma (pHGG) diagnosis portends poor prognosis and therapeutic monitoring remains difficult. Tumors release cell-free tumor DNA (cf-tDNA) into cerebrospinal fluid (CSF), allowing for potential detection of tumor-associated mutations by CSF sampling. We hypothesized that direct, electronic analysis of cf-tDNA with a handheld platform (Oxford Nanopore MinION) could quantify patient-specific CSF cf-tDNA variant allele fraction (VAF) with improved speed and limit of detection compared with established methods.

EXPERIMENTAL DESIGN

We performed ultra-short fragment (100-200 bp) PCR amplification of cf-tDNA for clinically actionable alterations in CSF and tumor samples from patients with pHGG (n = 12) alongside nontumor CSF (n = 6). PCR products underwent rapid amplicon-based sequencing by Oxford Nanopore Technology (Nanopore) with quantification of VAF. Additional comparison to next-generation sequencing (NGS) and droplet digital PCR (ddPCR) was performed.

RESULTS

Nanopore demonstrated 85% sensitivity and 100% specificity in CSF samples (n = 127 replicates) with 0.1 femtomole DNA limit of detection and 12-hour results, all of which compared favorably with NGS. Multiplexed analysis provided concurrent analysis of H3.3A (H3F3A) and H3C2 (HIST1H3B) mutations in a nonbiopsied patient and results were confirmed by ddPCR. Serial CSF cf-tDNA sequencing by Nanopore demonstrated correlation of radiological response on a clinical trial, with one patient showing dramatic multi-gene molecular response that predicted long-term clinical response.

CONCLUSIONS

Nanopore sequencing of ultra-short pHGG CSF cf-tDNA fragments is feasible, efficient, and sensitive with low-input samples thus overcoming many of the barriers restricting wider use of CSF cf-tDNA diagnosis and monitoring in this patient population.

Expression of the Androgen Receptor Governs Radiation Resistance in a Subset of Glioblastomas Vulnerable to Antiandrogen Therapy

New approaches are needed to overcome intrinsic therapy resistance in glioblastoma (GBM). Because GBMs exhibit sexual dimorphism and are reported to express steroid hormone receptors, we reasoned that signaling through the androgen receptor (AR) could mediate therapy resistance in GBM, much as it does in AR-positive prostate and breast cancers. We found that nearly half of GBM cell lines, patient-derived xenografts (PDX), and human tumors expressed AR at the transcript and protein level-with expression levels overlapping those of primary prostate cancer. Analysis of gene expression datasets also revealed that AR expression is higher in GBM patient samples than normal brain tissue. Multiple clinical-grade antiandrogens slowed the growth of and radiosensitized AR-positive GBM cell lines and PDXs in vitro and in vivo Antiandrogens blocked the ability of AR-positive GBM PDXs to engage adaptive transcriptional programs following radiation and slowed the repair of radiation-induced DNA damage. These results suggest that combining blood-brain barrier permeable antiandrogens with radiation may have promise for patients with AR-positive GBMs.

Everolimus improves the efficacy of dasatinib in PDGFRα-driven glioma

Pediatric and adult high-grade gliomas (HGGs) frequently harbor PDGFRA alterations. We hypothesized that cotreatment with everolimus may improve the efficacy of dasatinib in PDGFRα-driven glioma through combinatorial synergism and increased tumor accumulation of dasatinib. We performed dose-response, synergism, P-glycoprotein inhibition, and pharmacokinetic studies in in vitro and in vivo human and mouse models of HGG. Six patients with recurrent PDGFRα-driven glioma were treated with dasatinib and everolimus. We found that dasatinib effectively inhibited the proliferation of mouse and human primary HGG cells with a variety of PDGFRA alterations. Dasatinib exhibited synergy with everolimus in the treatment of HGG cells at low nanomolar concentrations of both agents, with a reduction in mTOR signaling that persisted after dasatinib treatment alone. Prolonged exposure to everolimus significantly improved the CNS retention of dasatinib and extended the survival of PPK tumor-bearing mice (mutant TP53, mutant PDGFRA, H3K27M). Six pediatric patients with glioma tolerated this combination without significant adverse events, and 4 patients with recurrent disease (n = 4) had a median overall survival of 8.5 months. Our results show that the efficacy of dasatinib treatment of PDGFRα-driven HGG was enhanced with everolimus and suggest a promising route for improving targeted therapy for this patient population.

The effect of postoperative complications on survival and recurrence after surgery for breast cancer: A systematic review and meta-analysis

BACKGROUND

This systematic review investigated the impact of complications on long term outcomes for patients with primary invasive operable breast cancer.

METHODS

A systematic review was performed using appropriate keywords, and meta-analysis using a random effects model completed.

RESULTS

Ten retrospective cohort studies, including 37,657 patients were included. Five studies identified a relationship between wound complications, infection and pyrexia and recurrence or recurrence-free survival. Risk of recurrence, 1-year and 5-year recurrence-free survival and overall survival were related to complications, particularly for patients with poor Nottingham Prognostic Index. Five studies failed to demonstrate a relationship between complications and prognosis. Complication was found to significantly affect 5-year recurrence-free survival (HR 1.48 95 % CI 1.02-2.14, p = 0.04) but not recurrence (HR 2.39, 95 %CI 0.94-6.07, p = 0.07), with a high degree of heterogeneity amongst analysed studies (I2 = 95 %).

DISCUSSION

Further research is needed to quantify the effects of postoperative complication on prognosis following surgery for breast cancer.

Abstract 6267: Repurposing antiandrogens to overcome therapy resistance in androgen receptor-positive glioblastoma

New approaches are needed to overcome intrinsic therapy resistance in glioblastoma (GBM). Because GBMs exhibit sexual dimorphism and are reported to express steroid hormone receptors, we reasoned that signaling through the androgen receptor (AR) could mediate therapy resistance in GBM, as it does in AR-positive prostate and breast cancers. Using RNAseq, immunoblot and immunohistochemistry, we found that nearly half of GBM cell lines, patient-derived xenografts and human tumors express AR transcript and protein with levels that overlap those of primary prostate cancer. AR expression in GBM did not vary by sex, age or common molecular alterations. We identified two cell line models of GBM that expressed AR protein (LN18 and T98G: termed “AR positive”) and two that did not (8MGBA and AM38: termed “AR negative”). Seviteronel, a blood-brain barrier permeable CYP17 lyase inhibitor and antiandrogen slowed growth in AR positive GBM cell lines (GI50 3-4 µM) but not AR negative lines (GI50 &gt; 500 µM) as measured by the colony formation assay. The antiandrogen enzalutamide, which also penetrates the blood brain barrier, similarly preferentially slowed growth in AR positive GBM cell lines. Seviteronel and enzalutamide sensitized AR positive GBM cell lines to radiation with enhancement ratios of 1.3-1.6 as measured by the clonogenic survival assay. Antiandrogens had no effect on the radiosensitivity of AR negative GBM cell lines. Seviteronel treatment did not affect the growth of AR positive T98G xenografts grown in vivo, but did sensitize these tumors to radiation (median time to tripling: 15 d with radiation alone and not reached with radiation combined with seviteronel). Enzalutamide similarly had modest single agent effects on an AR positive GBM patient-derived xenograft (GBM26 from the Mayo Clinic GBM PDX national resource) grown in vivo but sensitized these tumors to radiation (median time to tripling: 25.5 d with radiation alone and 39 d with radiation combined with enzalutamide). RNAseq performed on GBM26 tumors grown in vivo revealed that enzalutamide treatment caused minimal transcriptional changes when given as monotherapy but, when given in combination with radiation, blocked the ability of AR-positive GBMs to engage adaptive transcriptional programs related to multiple DNA repair pathways. We confirmed these mechanistic findings in vitro, as antiandrogens selectively impaired the repair of radiation-induced double strand DNA breaks in AR positive GBM cell lines. These results suggest that AR signaling may mediate therapy resistance in AR positive GBMs, and patients with these tumors could derive clinical benefit from combination therapies involving radiation and blood-brain-barrier permeable antiandrogens.

Citation Format: Christian K. Werner, Uchechi Nna, Hanshi Sun, Kari Wilder-Romans, Joseph Dresser, Ayesha Kothari, Weihua Zhou, Yangyang Yao, Arvind Rao, Stefanie Stallard, Carl Koschmann, Tarik Bor, Waldemar Debinski, Alexander Hegedus, Meredith Morgan, Sriram Venneti, Edwina Baskin-Bey, Daniel Spratt, Howard Colman, Jann Sarkaria, Arul Chinnayain, Joel Eisner, Corey Speers, Theodore S. Lawrence, Roy Strowd, Daniel R. Wahl. Repurposing antiandrogens to overcome therapy resistance in androgen receptor-positive glioblastoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6267.

PDTM-10. USE OF A NOVEL, HAND-HELD, ELECTRONIC DNA ANALYSIS PLATFORM TO QUANTIFY MULTI-GENE MOLECULAR RESPONSE IN CSF OF PATIENTS WITH HIGH-GRADE GLIOMA

BACKGROUND

For midline tumors, surgical biopsy risks neurological injury. Non-invasive methods for diagnosis and surveillance are greatly needed. Tumors release DNA into cerebrospinal fluid (CSF-ctDNA), allowing for potential detection and serial monitoring of tumor-associated genetic mutations by CSF sampling. Current detection platforms are limited by their requirement for assay development for each mutation (digital droplet PCR), or cost and timeliness (Illumina sequencing). We hypothesized that direct, electronic analysis of CSF-ctDNA with a novel, hand-held platform (Oxford Nanopore MinION) could provide real-time, ultra-deep sequencing of patient-specific alterations in CSF-ctDNA.

METHODS

We established multiple clinical trials for pediatric high-grade glioma with required multi-time point (0, 2, and 6 month) correlate lumbar puncture (LP) at time of MRI, with accrual ongoing. We performed amplicon-based PCR on CSF-ctDNA for recurrent mutations and sequenced patient samples (tumor tissue n=8, tumor CSF n=60) and normal controls (tissue n=5, CSF n=24) using NanoPore technology. Variant allele fractions (VAF) were determined via MinKNOW, Guppy, MiniMap2, and Integrated Genome Browser.

RESULTS

Sensitivity was 79% and specificity 100% by NanoPore. Time from LP to results was 12 hours. A 17-year-old female presented with a biopsy-proven grade IV thalamic glioma with clonal mutations in H3F3A K27M, PIK3CA E545G, TP53 R158G, and TP53 R248Q. After failing standard treatment, she was enrolled in the ONC201 clinical trial and underwent serial LPs. MRI showed stable tumor at 2 months and 40% decrease at 6 months of treatment. H3K27M VAF increased from baseline at 2 months, but decreased to 1% at 6 months of treatment, results that were confirmed by ddPCR. PIK3CA E545G, TP53 R158G, and TP53 R248Q demonstrated the same decrease in VAF, with p-value of < 0.0001.

CONCLUSIONS

We demonstrate a rapid, reliable method to detect tumor mutations in CSF, and further show molecular remission of H3K27M glioma by CSF sampling.

EXTH-47. THERAPEUTIC REVERSAL OF PRENATAL PONTINE ID1 SIGNALING IN DIPG

Diffuse intrinsic pontine gliomas (DIPGs) are lethal brain tumors with no effective therapies other than radiation. Inhibitor of DNA binding (ID) proteins are key regulators of tissue and lineage-specific gene differentiation during embryogenesis. Previous work has shown that H3F3A and ACVR1 mutations increase ID1 expression in cultured astrocytes, but this has not been validated in human DIPG, nor has the regulation and targetability of ID1 been explored in DIPG. Analysis of multi-focal post-mortem tumor and normal brain tissue (n=52) as well as multiple human datasets revealed ID1 to be elevated in DIPG. Elevated ID1 was found to correlate with reduced survival in DIPG. In a multi-focal autopsy DIPG case, we found ID1 expression to be heterogeneous and to correlate with tumor invasion. Chromatin immunoprecipitation-qPCR (ChIP-qPCR) was used to quantify H3K27ac and H3K27me3 at ID1 gene regulatory regions (promoters/enhancers) in multi-focal post-mortem tissue. The ID1 loci was found to be epigenetically poised for up-regulation (elevated H3K27ac and low H3K27me3) in DIPG tissue, regardless of H3 or ACVR1 mutation status, compared to normal brain. Analysis of publically-available ISH and ChIP-sequencing data revealed elevated ID1 expression and ID1-enhancer H3K27ac in prenatal mouse hindbrain compared to prenatal forebrain, prenatal midbrain, and all postnatal brain regions. ID1 shRNA-mediated knockdown of primary human H3K27M DIPG cells (DIPG007) resulted in significantly reduced invasion and migration. As cannabidiol (CBD) has successfully been used to therapeutically target ID1 in pre-clinical models of adult human cancers, we treated DIPG007 cells with CBD and found reduced viability at clinically relevant dosing (IC50=2.4 uM) with dose-dependent reduction in ID1 protein. ID1 knockdown and CBD treatment studies in murine models of DIPG are ongoing. These findings indicate that a multifactorial (genetic and regionally-based) epigenetic upregulation of ID1 drives DIPG invasiveness and is targetable with CBD.

PDCT-12. CLINICAL EFFICACY OF ONC201 IN THALAMIC H3 K27M-MUTANT GLIOMA

ONC201, the first bitopic DRD2 antagonist for clinical oncology, has shown efficacy in H3 K27M-mutant glioma. We performed an integrated preclinical and clinical analysis of ONC201 in thalamic H3 K27M-mutant glioma. ONC201 was effective in mouse intra-uterine electroporation (IUE)-generated H3 K27M-mutant gliomas, with an in vitro IC50 of 500 nM and 50% prolongation of median survival in vivo (p=0.02, n=14). Elevated DRD2 expression was found in the thalamus of non-malignant brain tissue, leading to the hypothesis that thalamic tumors may be a particularly ONC201-sensitive sub-group. We analyzed thalamic H3 K27M-mutant glioma patients treated with ONC201 as of the 05/22/2019 cutoff date, which included patients who had recurrent disease prior to initiating ONC201 (n=20; 15–73 years old) and post-radiation non-recurrent patients (n=11; 5–19 years old). As of 5/22/2019, 10 of 20 recurrent patients and 9 of 11 non-recurrent patients remain on-treatment. Median PFS has not been reached for either cohort: median follow-up of 2.2 months (range: 0.6–37.9) for recurrent patients and 10.6 months (range: 4.3–20.5) from diagnosis for non-recurrent patients. Best response so far by RANO includes 1 CR, 2 PR, 7 SD, 9 PD, 1 NE for recurrent patients and 1 PR, 7 SD, 3 PD for non-recurrent patients. Additionally, 3 recurrent (-66%, -47%, -34%) and 2 non-recurrent (-40%, -10%) patients experienced regressions but are not yet confirmed PRs. For recurrent patients, median onset of response is 3.5 months (range: 2.2–3.8) and median duration of response has not been reached with a median follow-up of 12.5 months (range: 8.1–32.8). Preliminary analyses demonstrated a strong correlation of cell-free tumor DNA in plasma and CSF with MRI response. In summary, ONC201 demonstrates promising clinical efficacy in thalamic H3 K27M-mutant glioma patients, regardless of age. Micro-environmental DRD2 expression may enhance the overall ONC201 response and extend its therapeutic utility beyond H3 K27M-mutant glioma.

Molecular profiling and targeted therapy in pediatric gliomas: review and consensus recommendations

As the field of neuro-oncology makes headway in uncovering the key oncogenic drivers in pediatric glioma, the role of precision diagnostics and therapies continues to rapidly evolve with important implications for the standard of care for clinical management of these patients. Four studies at major academic centers were published in the last year outlining the clinically integrated molecular profiling and targeting of pediatric brain tumors; all 4 demonstrated the feasibility and utility of incorporating sequencing into the care of children with brain tumors, in particular for children and young adults with glioma. Based on synthesis of the data from these studies and others, we provide consensus recommendations for the integration of precision diagnostics and therapeutics into the practice of pediatric neuro-oncology. Our primary consensus recommendation is that next-generation sequencing should be routinely included in the workup of most pediatric gliomas.

The effect of everolimus on CNS penetration and efficacy of dasatinib in the treatment of PDGFRA-driven glioma

e13508

Background: Pediatric and adult high-grade glioma (HGG) frequently harbor PDGFRA alterations. The CNS penetration of PDGFRA inhibitors, such as dasatinib, is limited by the tumor-efflux protein P-glycoprotein (P-gp). We hypothesized that co-treatment with everolimus, which has been shown to block P-gp, will increase CNS penetration and efficacy of dasatinib in in vitro and in vivo models as well as in human PDGFRA-driven glioma. Methods: Tumors were generated in mice using an intra-uterine electroporation (IUE) model [introduction of TP53, PDGFRA and H3K27M mutations in pre-natal cortex]. Dose response, synergism studies, P-GP inhibition and pharmacodynamics/pharmacokinetic studies were then performed on in vitro and in vivo models employing this IUE system. A phase 2 trial employing dasatinib and everolimus was established for children with HGG and diffuse intrinsic pontine glioma (DIPG) that contain PDGFRA alterations (NCT03352427). Paired CSF/plasma samples (before and after addition of everolimus) were collected from enrolled patients. Results: Dasatinib effectively treated mouse HGG cells with an IC50 of 100 nM. Dose-dependent reduction in PDGFRA and pPDGFRA was found. P-gp inhibitor assay confirmed that everolimus strongly blocks P-gp activity at 1 uM (p = 0.0028 vs untreated). Mice treated with dasatinib and everolimus had extended survival as compared to control. Two-hour exposure to everolimus resulted in sub-IC50 dasatinib concentration in cortex (23 nM) and tumor (65 nM). 24-hour exposure to everolimus resulted in greater cortex (235 nM) and tumor (509 nM) concentrations. Two trial patients, recurrent HGG ( PDGFRA-amplified) and recurrent DIPG ( PDGFRA D842V) respectively, survived 6 months and 9 months (ongoing) after progression, which compares very favorably to historical controls. A paired CSF sample from the PDGFRA-amplified patient showed a 50% increase in CSF dasatinib level after addition of everolimus. Conclusions: Dasatinib treatment of PDGFRA-driven HGG is improved with everolimus blockade of P-gp and represents a novel route for improving CNS penetration and efficacy of therapies for HGG. Clinical trial information: NCT03352427.

Medulloblastoma therapy generates risk of a poorly-prognostic H3 wild-type subgroup of diffuse intrinsic pontine glioma: a report from the International DIPG Registry

With improved survivorship in medulloblastoma, there has been an increasing incidence of late complications. To date, no studies have specifically addressed the risk of radiation-associated diffuse intrinsic pontine glioma (DIPG) in medulloblastoma survivors. Query of the International DIPG Registry identified six cases of DIPG with a history of medulloblastoma treated with radiotherapy. All patients underwent central radiologic review that confirmed a diagnosis of DIPG. Six additional cases were identified in reports from recent cooperative group medulloblastoma trials (total n = 12; ages 7 to 21 years). From these cases, molecular subgrouping of primary medulloblastomas with available tissue (n = 5) revealed only non-WNT, non-SHH subgroups (group 3 or 4). The estimated cumulative incidence of DIPG after post-treatment medulloblastoma ranged from 0.3-3.9%. Posterior fossa radiation exposure (including brainstem) was greater than 53.0 Gy in all cases with available details. Tumor/germline exome sequencing of three radiation-associated DIPGs revealed an H3 wild-type status and mutational signature distinct from primary DIPG with evidence of radiation-induced DNA damage. Mutations identified in the radiation-associated DIPGs had significant molecular overlap with recurrent drivers of adult glioblastoma (e.g. NRAS, EGFR, and PTEN), as opposed to epigenetic dysregulation in H3-driven primary DIPGs. Patients with radiation-associated DIPG had a significantly worse median overall survival (median 8 months; range 4-17 months) compared to patients with primary DIPG. Here, it is demonstrated that DIPG occurs as a not infrequent complication of radiation therapy in survivors of pediatric medulloblastoma and that radiation-associated DIPGs may present as a poorly-prognostic distinct molecular subgroup of H3 wild-type DIPG. Given the abysmal survival of these cases, these findings provide a compelling argument for efforts to reduce exposure of the brainstem in the treatment of medulloblastoma. Additionally, patients with radiation-associated DIPG may benefit from future therapies targeted to the molecular features of adult glioblastoma rather than primary DIPG.

Population-based study of the sensitivity of axillary ultrasound imaging in the preoperative staging of node-positive invasive lobular carcinoma of the breast

BACKGROUND

Preoperative staging of the axilla is important to allow decisions regarding neoadjuvant treatment and the management of the axilla. Invasive lobular carcinoma metastases are difficult to detect because of the infiltrative pattern of the nodal spread. In this study the sensitivity of preoperative axillary staging between invasive lobular (ILC) and ductal (IDC) carcinoma was compared.

METHODS

All women diagnosed with pure ILC or IDC in the West of Scotland in 2012-2014 were identified from a database maintained prospectively within the Managed Clinical Network. Pretreatment axillary ultrasound imaging (AUS), core biopsy and fine-needle aspiration cytology (FNAC) results were compared between ILC and IDC.

RESULTS

Some 602 women with ILC and 4199 with IDC had undergone axillary surgery, of whom 209 and 1402 respectively had nodal metastases. Pretreatment AUS sensitivity was significantly lower in ILC than in IDC (32·1 versus 50·1 per cent respectively, P < 0·001; OR 0·47, 95 per cent c.i. 0·34 to 0·64). Core biopsy had equally high sensitivity of 86 per cent in both subtypes; however, FNAC was significantly less sensitive in both ILC (55 per cent; P = 0·003) and IDC (75·6 per cent; P = 0·006). Multivariable analysis revealed that cT3-4 status and symptomatic presentation were both significant in predicting nodal metastasis in patients with ILC and false-negative AUS findings (OR 3·77, 95 per cent c.i. 1·69 to 8·42, P = 0·001; and OR 1·92, 1·24 to 2·98, P = 0·003, respectively).

CONCLUSION

AUS is inferior in detecting axillary node metastasis in ILC compared with IDC. Women with cT3-4 lobular carcinoma may benefit from ultrasound-guided axillary biopsy regardless of the ultrasonographic appearance of the nodes.

Abstract P4-13-01: Oncoplastic breast conservations – The Scottish Audit: Surgical techniques, oncological outcomes, complication rates and variations in practice across the country based on the analysis of 589 patients

Introduction: current evidence for oncoplastic breast conservation (OBC) is based on single institutional series. We studied the outcomes of OBC practice in Scotland and compare individual breast units.

Methods: a predefined database of patients treated with OBC was completed retrospectively in 11 breast units in Scotland. Patients were treated with OBC from 2005 onwards were included. For statistical calculations Chi-test, ANOVA and Pearson correlation analysis were used.

Results: Altogether 589 patients were included. Median age was 56 years [21-86]. Patients were diagnosed between September 2005 and March 2017. Number of patients treated with OBC per unit ranged between 4 and 145. High volume units were doing a mean of 19.3 OBCs per year [17.3 – 26.5] vs. low volume units doing 11.1 OBCs per year [7 .7– 14.4] (p=0.012).

23 different oncoplastic surgical techniques were applied. Range of oncoplastic techniques used was associated with case-loads: high volume units used a wider range (8 – 14 different techniques) compared to low volume units (3 – 6) (p=0.004). Volume displacement was done in 515 patients (91.3%), volume replacement in 49 patients (8.7%). OBC was carried out as a joint operation between a breast and a plastic surgeon in 66.3% (389 patients). Immediate contralateral symmetrisation rate was significantly higher when the procedure was carried out as a joint operation (70.7% vs. not joint operations: 29.8%; p&lt;0.001).

Incomplete excision rate was 10.4% (60 of 578). Incomplete excision was significantly higher after invasive lobular carcinoma (18.9%; 10 of 43; p=0.0292). After neoadjuvant chemotherapy incomplete excision rate was significantly lower (3%; 2 of 66 vs. no neoadjuvant chemotherapy: 11%; 35 of 319; p=0.031).

Neodjuvant systemic treatment rate was 28.6% (142 of 496 patients). Of those 68 patients received neoadjuvant chemotherapy (13.7%) and 74 patients had neoadjuvant hormonal treatment (14.9%). Neoadjuvant systemic treatment rate varied amongst the units from 9.7% to 57.2% for patients with invasive carcinoma.

259 patients diagnosed with (non)invasive carcinoma had a median follow-up time of 5 years [35-124]. Of these 7 patients (2.7%) developed isolated local recurrence. 5-year local recurrence rate after DCIS was higher than after pure invasive ductal carcinoma (DCIS: 8.3%; 3 of 36 vs. ductal: 1.6%; 3 of 181; p=0.02567). 5-year disease-free survival of these patients was 91.7%, overall survival was 93.8%, and cancer-specific survival was 96.1%.

145 of 510 patients developed complications, which is 28.4% overall complication rate. 71 patients had major complications (13.9%) and 74 patients had minor complications (14.5%). Overall complication rate was significantly lower after neoadjuvant chemotherapy (15.9%; 11 of 69) compared to patients who did not receive neoadjuvant chemotherapy (27.9%; 127 of 455 patients) (p=0.035).

Conclusion: this national audit demonstrated similar outcomes overall compared to relevant published data. Units should be urged to build stronger collaboration in order to reduce variability in OBC practices.

None of the authors have conflict of interest to declare.

Citation Format: Romics L, Macaskill J, Fernandez T, Morrow E, Simpson L, Pitsinis V, Barber M, Tovey S, Masannat Y, Young O, Mansell J, Stallard S, Doughty J, Dixon M. Oncoplastic breast conservations – The Scottish Audit: Surgical techniques, oncological outcomes, complication rates and variations in practice across the country based on the analysis of 589 patients [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P4-13-01.

Climbing Bloom's taxonomy pyramid: Lessons from a graduate histology course

Bloom's taxonomy was adopted to create a subject-specific scoring tool for histology multiple-choice questions (MCQs). This Bloom's Taxonomy Histology Tool (BTHT) was used to analyze teacher- and student-generated quiz and examination questions from a graduate level histology course. Multiple-choice questions using histological images were generally assigned a higher BTHT level than simple text questions. The type of microscopy technique (light or electron microscopy) used for these image-based questions did not result in any significant differences in their Bloom's taxonomy scores. The BTHT levels for teacher-generated MCQs correlated positively with higher discrimination indices and inversely with the percent of students answering these questions correctly (difficulty index), suggesting that higher-level Bloom's taxonomy questions differentiate well between higher- and lower-performing students. When examining BTHT scores for MCQs that were written by students in a Multiple-Choice Item Development Assignment (MCIDA) there was no significant correlation between these scores and the students' ability to answer teacher-generated MCQs. This suggests that the ability to answer histology MCQs relies on a different skill set than the aptitude to construct higher-level Bloom's taxonomy questions. However, students significantly improved their average BTHT scores from the midterm to the final MCIDA task, which indicates that practice, experience and feedback increased their MCQ writing proficiency. Anat Sci Educ 10: 456-464. © 2017 American Association of Anatomists.

Oncoplastic breast conservation surgery is oncologically safe when compared to wide local excision and mastectomy

BACKGROUND

Support for the oncological safety of oncoplastic breast conservation surgery (OBCS) is mostly based on evidence comparing recurrence rates after OBCS to wide local excision (WLE). However, OBCS is often indicated for larger cancers and oncological results should also be compared to patients treated with mastectomy. In this study we compared recurrence and survival following OBCS, mastectomy and WLE.

METHODS

Patients treated with OBCS between 2009 and 2012 were identified from a prospectively maintained database. For comparison, consecutive patients treated with WLE or mastectomy with or without immediate reconstruction (Ms ± IR) over the same time period were identified. Histological variables of patients were compared using Fisher Exact or Chi squared tests, and recurrence and survival were compared using Kaplan-Meier and Cox regression survival analysis.

RESULTS

980 patients' data were analysed (OBCS: n = 104; WLE: n = 558; Ms ± IR: n = 318). Tumour size, grade, nodal status, ER, and PR expression of patients treated with OBCS were all significantly more adverse compared with patients treated with WLE (p < 0.001). These histological variables were similar in patients treated with Ms ± IR and OBCS. 5-year local recurrence rates were similar in all three groups (WLE: 3.4 per cent, OBCS: 2 per cent, Ms ± IR: 2.6 per cent; log rank = 0.973), while distant recurrence rates were higher after Ms ± IR and OBCS (Ms ± IR:13.1 per cent, OBCS:7.5 per cent, WLE:3.3 per cent; log rank: p < 0.001).

CONCLUSION

OBCS is oncologically safe in patients even when histological results are similar to patients treated with Ms ± IR.

Abstract P2-12-14: Therapeutic mammoplasty reduces high incomplete excision rate in lobular cancer

Introduction: Incomplete excision rate for lobular cancer is much higher compared to other types of breast cancer, since lobular cancer is frequently occult on imaging. This, and the inability to downstage lobular cancer with neoadjuvant therapy lead to the highest mastectomy rate of all subtypes. Here, we investigated the association between histopathological characteristics and incomplete excision as well as mastectomy rates.

Further, we investigated whether the application of level 2 therapeutic mammoplasty (TM) would extend the indication for conservation with lobular cancers.

Methods: Data of 1389 consecutive patients underwent surgery for (non)invasive breast cancer between January 2008 and June 2012 was analysed. Pathological and preoperative radiological results were analysed in the context of final surgery and tumour excision margins. Statistical significance was calculated using Chi-square, Mann-Whitney and Z-tests with a significance&lt;0.05.

Results: Overall incomplete excision rate was 13.74% (131/953), and mastectomy rate was 35.35% (491/1389). Higher incomplete excision and mastectomy rates were strongly associated with lobular subtype (IE: 26.03% (19/73)); M: 51.22% (63/123); p&lt;0.01 vs. other subtypes), node positivity (IE: 25% (36/144) vs. 10.43% (68/652); p=0 and M: 60.69% (193/318) vs. 25.65% (216/842); p=0) and tumour size (IE:T3 80% (4/5) vs. T2 22.51% (43/191) vs. T1 9.23% (55/596); all p&lt;0.01; and M: T3 95.35% (41/43) vs. 59.46% (242/407) vs. 16.16% (112/693); all p=0). Incomplete excision rates were independent of hormonal and HER-2 expressions (ER+: 12.55% (89/709) vs. ER-: 16.67% (15/90); p=0.27 and HER2 neg.: 12.67% (91/718) vs. HER2 pos.: 16.67% (13/78); p=0.32) and it was just higher in grade 2 and 3 cancers (14.6% (60/411); p=0.037 and 16.22% (36/222); p=0.021 vs. G1:6.86% (7/102). However, hormonal and HER-2 expressions as well as tumour grade were in strong association with mastectomy rate (ER pos.: 33.28% (335/1007) vs. ER neg.: 48.75% (78/160); p&lt;0.01; HER2 neg.: 33.43% (341/1020) vs. HER2 pos.: 49.65% (71/143); p&lt;0.01; G3: 50.49% (205/406) vs. G2: 30.77%(172/559) vs. G1: 14.28% (17/119); all p=0).

135 patients underwent surgery for lobular cancer (simple wide excision: 66; TM:19; mastectomy: 50). TM was offered for significantly larger tumours than lumpectomy (28.29mm (10-62) vs. 19.96mm(5-57);p&lt;0.01; vs. mastectomy: 37.56 mm(5-110);p=0.096). Incomplete margins were found with significantly smaller tumours when lumpectomy was applied compared to TM(25.94 mm(6-56) vs. 38.6 mm(30-45);p=0.031). Conservation was achieved with significantly bigger tumours when TM was used (25.46mm (10-62) vs. 17.66mm (5-57); p=0.032). Multifocality, however, significantly increased the chance for incomplete excision even after TM (4/7; p=0.019).

Conclusion: Higher incomplete excision rate is strongly associated with lobular subtype, node positivity and tumour size, but independent of hormonal end HER-2 expression, while tumour grade is not a strong predictor. All histopathological characteristics are strong predictors of final mastectomy rate. Using TM, breast conservation can be achieved for significantly larger lobular cancers, and incomplete excision rate decreased in smaller cancers, which are routinely treated with wide excision.

Citation Format: Romics L, Kabir SA, Mansell J, Mallon EA, Stallard S, Doughty JC. Therapeutic mammoplasty reduces high incomplete excision rate in lobular cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-12-14.

How to compare the oncological safety of oncoplastic breast conservation surgery - To wide local excision or mastectomy?

BACKGROUND

Comparative studies suggest that patients treated with oncoplastic breast conservation surgery (OBCS) have similar pathology to patients treated with wide local excision (WLE). However, patients treated with OBCS have never been compared to patients treated with mastectomy. The aim of this study was to identify which control group was comparable to patients undergoing OBCS.

METHODS

Commonly reported histopathological variables of patients treated with OBCS, WLE or mastectomy ± immediate reconstruction (Ms ± IR) were compared using Fisher Exact or Chi squared tests.

RESULTS

1000 patients' data were analysed (OBCS: n = 119; WLE: n = 600; Ms ± IR: n = 281). Tumour size was significantly bigger after OBCS than WLE (p < 0.001), but similar to Ms ± IR (p = 0.138). Tumour grade was higher after OBCS than WLE (p < 0.001), but similar to Ms ± IR (p = 0.497). More axillary nodes were involved in patients with OBCS than WLE (p < 0.001), but comparable to Ms ± IR (p = 0.175). ER and PR expressions were lower after OBCS compared to WLE (p = 0.007, p = 0.009), but identical to Ms ± IR (p = 1, p = 0.904 respectively). Differences in application of systemic (neo)adjuvant therapy followed the above trend.

CONCLUSION

Striking similarities found between OBCS and mastectomy patients' histopathological results are in sharp contrast with previously published data. This study suggests that oncological outcomes following OBCS should be compared to mastectomy besides WLE.

Abstract P5-15-07: Therapeutic mammaplasty - Radical breast conservation or conservative mastectomy? A comperative analysis of 1000 patients’ pathology results

Background: oncological principles of therapeutic mammaplasty (TM) is based on evidence arising from studies on the oncological safety of traditional breast conservation, i.e. wide local excision (WLE). Hence, oncological safety of TM is benchmarked to patients treated with WLE. However, TM can also be defined as a conversion of mastectomy (Ms) to breast conservation surgery applying plastic surgical techniques in patients conventionally requiring mastectomy. The aim of this study was to decide if TM was similar to WLE or Mx in terms of pathological characteristics.

Methods: 1006 consequtive patients were involved in the analysis, who were treated with TM, WLE or Ms in two Glasgow breast units between 2008 and 2011. Histopathological characteristics of patients treated with TM were compared to those treated with WLE or Ms. Statistical calculations were carried out with Chi-square test. The difference was considered statistically significant if p&gt;0.05.

Results: 121 patients were treated with TM, while 600 patients were treated with WLE and 285 with Ms. Tumour size of TM was significantly different from WLE as well as Ms, although the difference between TM and WLE was more significant than between TM and Ms (TM/Ms/WLE: T1: 43.8%, 34%, 78%; T2: 52.1%, 54.7%, 21%; T3: 4.1%, 11.2%, 1%; TM vs. WLE: p&lt;0.001; vs. Ms: p = 0.03). Tumour grade of TM was significantly higher than grade of WLE, but there was no significant difference between the grades of TM and Ms (TM/Ms/WLE: G1: 6.4%, 4.5%, 19.3%; G2: 37.6%, 41.8%, 54.8%; G3: 56%, 53.7%, 26%; TM vs. SZE: p&lt;0.001; vs. Ms: p = 0.625). Similarly, significantly more axillary nodes were involved in patients treated with TM compared to patients with WLE, while the same was comparable in patients with TM and Ms (TM/Ms/WLE: 0: 73.5%, 70.4%, 87.7%; 1-3: 24.5%, 25.6%, 12.2%; &gt;3: 2%, 4%, 0.2%; TM vs. WLE: p&lt;0.001; vs. Ms: p = 0.601). In terms of histological subtypes, again, there was a significant difference between TM and WLE, but we found no difference when TM was compared to Ms (TM vs. WLE: p = 0.027; vs. Ms: p = 0.582). There was statistically significantly more ER and/or PR positive patients in the group treated with WLE compared to TM (ER/PR TM vs. WLE p = 0.012 / = 0.014), but ER/PR expression was similar in TM and Ms patients (ER/PR TM vs. Ms p = 0.890 / = 0.635). While the trend above was similar in HER-2 expression pattern, there was no statistically significant difference could be demonstrated in between the groups (table).

Discussion: pathological characteristics of patients treated with therapeutic mammaplasty is similar to patients treated with mastectomy, but significantly different from patients who were treated with WLE. Pathology after WLE is significantly more favourable compared to TM. Hence, studies investigating oncological safety of TM comparing to patients treated with WLE only may not be adequate, and Ms patients should be included in the analyses.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-15-07.

Use of boost radiotherapy in oncoplastic breast-conserving surgery - a systematic review

BACKGROUND

The use of local boost radiotherapy to the tumour bed has been demonstrated in randomised-controlled trials to reduce local recurrence rates following breast-conserving surgery (BCS) and is the standard of care. Oncoplastic BCS techniques with parenchymal rearrangement present new challenges to the localisation of the tumour bed and therefore delivery of local boost radiotherapy. The aim of this review was to evaluate the reporting of boost radiotherapy in the oncoplastic BCS literature.

METHODS

Pubmed, Ovid MEDLINE, EMBASE, and the Cochrane Database of Systematic Reviews were searched for studies reporting oncoplastic BCS using volume displacement techniques.

RESULTS

24 studies met the inclusion criteria (n = 1933 patients). Use of boost radiotherapy was reported in 11 studies, in 2 of which it was for the treatment of incomplete or close margins, and marking of the tumour bed was only reported in 8 studies. None of the studies reported the number of patients where the tumour bed could not be localised.

CONCLUSIONS

The use of local boost radiotherapy and tumour bed marking was not reported in the majority of studies of oncoplastic BCS. Future studies need to provide detailed information regarding the use of boost radiotherapy and difficulties determining the target volume so that current radiotherapy approaches can be reviewed and improved for these advanced techniques.

Oncoplastic breast conservation does not lead to a delay in the commencement of adjuvant chemotherapy in breast cancer patients

INTRODUCTION

There is hardly any evidence that oncoplastic breast conservation surgery (OBCS) does not lead to a delay in the commencement of adjuvant chemotherapy. Although this is an integral part of overall oncological safety, no controlled studies have been published so far. Therefore, our aim was to determine whether OBCS led to a delay when compared to simple wide local excision (WLE), mastectomy (Ms) or mastectomy with immediate reconstruction (MsIR).

METHODS

Breast cancer patients who required adjuvant chemotherapy after OBCS, WLE, Ms and MsIR were identified from prospectively maintained institutional databases. Time between multidisciplinary team decision to offer chemotherapy and delivery of first cycle of chemotherapy was measured and compared among the four groups of patients.

RESULTS

time to chemotherapy of breast cancer patients (n = 169) treated with OBCS (n = 31) were 29 [16-58] days, while it was 29.5 [15-105] days after WLE (n = 66), 29 [15-57] days after Ms (n = 56) and 31 [15-58] days after MsIR (n = 16). A combined analysis involving all four groups demonstrated no statistically significant difference (p = 0.524). Similarly, inter-group analysis revealed no significant differences in between patients treated with OBCS compared to any of the three control groups (OBCS to WLE: p = 0.433; OBCS to Ms: p = 0.800; OBCS to MsIR: p = 0.405).

CONCLUSION

OBCS seems as safe as WLE, Ms or MsIR in terms of delivery of adjuvant chemotherapy, and, therefore, should not adversely affect breast cancer outcome in this respect.

Abstract P4-14-13: Therapeutic mammaplasty does not cause a delay in the delivery of chemotherapy in high risk breast cancer patients

Introduction: oncosurgical safety of therapeutic mammaplasty (TM) is widely investigated. The interval between surgery and delivery of adjuvant chemotherapy is an integral part of overall oncological safety. Therefore, we examined the time between TM and AC, and compared it to wide local excision (WLE) and mastectomy (Mx) with or without immediate breast reconstruction (IBR), respectively.

Methods: data of 174 patients who underwent TM, WLE and Mx±IBR was analyzed retrospectively. All patients were operated within three breast units of Glasgow during a period of 48 months. Time between decision to offer adjuvant chemotherpay and delivery of the first cycle of chemotherapy was analyzed. Significance was calculated with Mann-Whitney and Kruskal-Wallis tests (two and four groups compared, respectively).

Results: median time to adjuvant chemotherapy after TM (n = 36) was 29 [16–58] days, WLE (n = 66) was 29.5 [15–105], Mx only (n = 56) was 29 [15–57], and Mx and IBR (n = 16) was 31 [15–58] days. No significant difference was found in terms of time to adjuvant chemotherpay in patients treated with TM compared to WLE (p = 0.384), Mx only (p = 0.828) or Mx and IBR (p = 0.366). Further, there was no significant difference when a cumulative comparison of the four groups was carried out (p = 0.507).

Conclusions: our data indicate that oncosurgical safety of TM in terms of time to chemotherapy is similar to other high risk breast cancer patients treated WLE and Mx with or without IBR. This also suggests that there is no significant difference in postoperative complication rates after these four ways of surgical treatment of breast cancer, which would possibly be the primary cause for a delay in delivering adjuvant chemotherapy.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P4-14-13.

Ten-year follow-up of skin-sparing mastectomy followed by immediate breast reconstruction

BACKGROUND

The oncological safety of skin-sparing mastectomy (SSM) followed by immediate breast reconstruction (IBR) is debated owing to a presumed compromise in the completeness of mastectomy. Current evidence is poor as it is based mostly on short-term follow-up data from highly selected patients.

METHODS

A prospectively maintained institutional database was searched to identify patients who underwent SSM and IBR between 1995 and 2000. A retrospective review of medical records was carried out, including only patients with ductal carcinoma in situ and invasive breast cancer. During this time all patients treated with mastectomy were offered IBR regardless of tumour stage.

RESULTS

Follow-up data from 253 consecutive patients with IBR were reviewed. Patients with incomplete follow-up data and those undergoing SSM for recurrent disease following previous lumpectomy were disregarded, leaving 207 for analysis. Offering IBR to all women requiring mastectomy resulted in a large proportion of patients with advanced disease. During a median follow-up of 119 months, 17 (8·2 per cent) locoregional, six (2·9 per cent) local and 22 (10·6 per cent) distant recurrences were detected; the overall recurrence rate was 39 (18·8 per cent). Overall recurrence rate was associated with axillary lymph node metastasis (P = 0·009), higher stage (P < 0·001) and higher tumour grade (P = 0·031). The breast cancer-specific survival rate was 90·8 per cent (19 of 207 women died from recurrence).

CONCLUSION

Based on these long-term follow-up data, SSM combined with IBR is an oncologically safe treatment option regardless of tumour stage.

P2-16-11: Role of Proper Patient Counselling in Combination with Effect of Socioeconomic Deprivation on the Rate of Immediate Breast Reconstruction after Mastectomy

Introduction: current guidelines in the United Kingdom suggest that the possibility of breast reconstruction should be discussed with all patients prior to mastectomy. However, the majority of patients are still treated with mastectomy alone and no reconstruction is carried out. It has also been suggested that women from more deprived areas are less likely to undergo immediate breast reconstruction (IBR). We investigated potential pitfalls in patient counselling and consequent decision making contributing to present IBR rate in combination with the effect of socioeconomic deprivation.

Methods: data from 89 consecutive mastectomy patients was prospectively collected in a single centre in Glasgow between August 2010 and March 2011. Each patient was scored for deprivation based on The Scottish Index of Multiple Deprivation. The patients were then divided into two groups: high and low deprivation levels. Consultations about IR and patients’ acceptance of counselling were analysed. For statistical calculations Fischer's exact test was applied. Results: IBR was offered to 41 (46%) patients, but it was not to 42 (47%) (6 were excluded due to incomplete data). 25 patients accepted IBR, and of those 24 (27%) underwent IBR. 16 of 41 patients refused to undergo IBR due to lack of interest (10), not feeling ready for it (2), preference of delayed procedure (2) and fear of delaying adjuvant therapy (2). Of 42 patients whom IBR was not offered, only 10 were documented in the notes, while there was no reference for discussing reconstruction in 32 (36%) cases. Reasons for not even discussing reconstruction were the following: age (15), co-morbidities (18), locally advanced cancer (2), co-morbidities with age (5), and locally advanced cancer with age (2). As regards to socioeconomic deprivation; 44 (49%) patients were from deprived areas and 39 (44%) from affluent areas. 41 patients were offered IBR and of these 23 (26%) were from affluent areas compared to 18 (20%). Of the 42 patients who were not offered IR, 26 (29%) were from deprived while 16 (18%) from affluent areas (p&lt;0.05). Of the 44 deprived patients, 18 were offered IBR but 26 were not. 15 of 25 patients, who accepted IBR, were from affluent areas. The 16 patients who refused IBR had equal distribution of deprivation.

Conclusions: while none of the reasons for not offering IBR represent absolute contraindication to IBR, decisions about refusal are based mostly on patients’ subjective intuitions. Further, a greater proportion of the patients who were not offered IBR were from more deprived areas, and it seems that patients from affluent areas are more likely to be offered IBR compared to ones from deprived areas. However, confounding factors such as co-morbidities may contribute to the above. We believe, therefore, that detailed counselling about reconstruction of each patient requiring mastectomy is necessary, which is likely to further increase IBR rate.

Impact of national guidelines on family history breast cancer surveillance

The breast cancer risk of women already under family history surveillance was accurately assessed according to national guidelines in an attempt to rationalize the service. Women attending two breast units in Glasgow between November 2003 and February 2005 were included. One thousand and five women under annual surveillance were assessed and had their relatives diagnoses verified. Four hundred and ninety-seven women were at significantly increased risk and eligible for follow-up. Five hundred and eight (50%) women attending were not eligible for family history surveillance, and 498 (98%) of these women accepted discharge. In conclusion, national guidelines have helped to more clearly define women who should undergo surveillance. This avoids unnecessary and potentially harmful routine investigations, and the service has been improved.

HER2 positive early breast cancers: tumour demographics and trastuzumab therapy in the real-world

Abstract #3159

Background: Various trials have shown substantial benefits of addition of Trastuzumab (Herceptin®) to adjuvant chemotherapy in Early Breast Cancer (EBC). We analysed our breast cancer population to determine the incidence of HER2 positive Early Breast Cancers, the tumour demographics and the number of patients eligible for and receiving trastuzumab therapy in this group.&#x2028; Methods: Data for all patients diagnosed with EBC in 2006 was recorded prospectively in a database. Case notes were consulted where the HER2 positive patients, determined by a combination of IHC and FISH, had not received trastuzumab, to ascertain the reasons.&#x2028; Results: A total of 951 patients were diagnosed with Breast Cancer in 2006. 417 (43.9%) of these were screen-detected cancers.&#x2028; There were 123 (12.9%) HER2 positive newly diagnosed Breast Cancers of whom 117 were EBCs. The HER2 positivity rate in the screen detected cancers (n=417) was 9% and 17% in the symptomatic cancers (n=433).&#x2028; 1. Demographics of the HER2 positive Early Breast Cancer Population:&#x2028; The median age at diagnosis was 61 yrs (range: 30-92).&#x2028; &#x2028; 2. Fifty nine (50.4%) of the HER2 positive EBCs received trastuzumab therapy.&#x2028; &#x2028; Conclusions: The HER2 positivity rate is lower than that previously reported suggestive of changing demographics secondary to a high screen detected cancer population. A third of the HER2 positive tumours are screen detected. The percentage of ER positive, node negative and low grade tumours was higher than anticipated.&#x2028; Only 50% of HER 2 positive EBC patients received trastuzumab therapy. Of those who did not receive trastuzumab, the commonest reason was low risk status or age and co-morbidities precluded chemotherapy.&#x2028; HER 2 positivity alone confers high risk irrespective of pathological stage. Further trials are required to evaluate whether the substantial number of patients who are at present not eligible for trastuzumab therapy might also benefit.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3159.